After dispensing of some of their contents plastic tubes usually tend to suck in ambient air due to recovery of the tube container which causes a negative pressure inside the tube. The ambient air can react with the contents of the tube container, in particular if the contents are oxygen-sensitive. The fill level of the tube can typically not be inspected visually, as the tube container retakes its original shape due to the sucked in ambient air.
Furthermore, dispensing very liquid contents as drops from known tubes is often not possible as the potentially high internal pressure can lead to the drops being dispensed too fast or in form of a jet.
Japanese patent application JP 2004-034996 A discloses a tube with a tube container, a tubular mouth and a cap member. When the cap member is mounted on the tubular mouth such that an internal space of the tubular mouth is hermetically sealed, a vent passage is formed inside the cap member and around the outer periphery of the tubular mouth, respectively. When the cap member is removed, the internal space of the tubular mouth can communicate with the ambient air via the vent passage such that the contents of the tube container are not accidentally sucked out due to negative pressure.
From the German patent application DE 102 13 124 A1 there is known a valve for automatically closing a tube. The valve has radial slots on the inside and on the outside at a lower level. Radially outwardly projecting stars are formed at an upper level of the valve. For mounting in a tube mouth the valve is turned inside out. The radial slots then serve as anchoring means for fastening the valve at the lower end of the tube mouth. The stars are now inwardly projecting and form a sealing rosette-shaped valve. For fixating the rosette-shaped valve a clamping collar is employed.
Patent document U.S. Pat. No. 7,222,751 B2 relates to collapsible tubes for storing and distributing liquid to pasty products keeping them protected from ambient air. A tube head is disclosed that is fitted with a non-return valve to prevent pollution from ambient air due to relaxation of the pressure on the skirt. The valve is inserted in the neck of the tube head. The valve comprises a sealing means that is in contact with a ring support having an opening. The sealing means is connected to an elastically deformable support element. The sealing means closes the opening when the tube is not compressed. When pressure is applied to the skirt of the tube, the product applies pressure on the sealing means and the sealing means is lifted. When the pressure is removed, the elastic return of the skirt causes a negative pressure that pushes the sealing means into contact with the ring support thereby closing the opening.
Known valves by which the entrance of ambient air into the tube container can be prevented after contents have been dispensed usually require a lot of space inside the tube neck. The known valves often consist of two parts and their sealing area is not adjustable so that the known valves often suffer from insufficient sealing properties. The known valves usually have to be mounted separately which leads to additional and often high costs.